CN109781914B

CN109781914B - QuEChERS method for detecting pesticide residue based on purifying agent state switching

Info

Publication number: CN109781914B
Application number: CN201910199871.3A
Authority: CN
Inventors: 张志琪; 王军; 段慧玲
Original assignee: Shaanxi Normal University
Current assignee: Shaanxi Normal University
Priority date: 2019-03-15
Filing date: 2019-03-15
Publication date: 2021-07-23
Anticipated expiration: 2039-03-15
Also published as: CN109781914A

Abstract

The invention discloses a QuEChERS method for detecting pesticide residue based on purifying agent state switching, wherein the molecular structure of the purifying agent simultaneously contains amino and C₁₀～C₂₀Alkyl, and the melting point is 30-60 ℃, and the alkyl is slightly soluble or insoluble in acetonitrile at the temperature of below 0 ℃. The method comprises the steps of dehydrating an acetonitrile extraction liquid of a sample to be detected, adding a purifying agent, controlling the temperature to be higher than the melting point of the purifying agent, fully reacting the melted purifying agent with an acetonitrile extraction liquid to perform dispersion liquid-liquid microextraction, then reducing the temperature to solidify the purifying agent, separating the solidified purifying agent combined with a large amount of impurities from the extraction liquid through centrifugation or filtration, thereby achieving the purposes of removing the impurities and purifying a sample matrix, and finally directly introducing the purified extraction liquid into a gas chromatography-mass spectrometer for detection and analysis. The method has the characteristics of high extraction efficiency, high enrichment rate, small using amount of the purifying agent and the like, and the purifying agent is converted into a solid phase for separation, so that the defect of incomplete liquid-liquid microextraction separation of the dispersion liquid is avoided.

Description

QuEChERS method for detecting pesticide residue based on purifying agent state switching

Technical Field

The invention belongs to the technical field of analytical chemistry, and particularly relates to a QuEChERS method for detecting pesticide residues in foods such as vegetables and fruits by using substances with switchable states under mild conditions as purification materials.

Background

With the large-scale use of pesticides, the harm caused by pesticide residues is more and more serious, the maximum limit of pesticide residues in food is strictly limited by related laws and regulations, related detection and analysis methods are rapidly developed for controlling and detecting the pesticide residues, and the detection of the pesticide residues in food is always the focus of attention of researchers. The sample pretreatment process is particularly important when analyzing drug residues in food such as fruits, vegetables, meat, grains, milk, tea leaves and the like. The traditional sample pretreatment method mainly comprises liquid-liquid extraction, solid-phase microextraction, matrix solid-phase dispersion extraction and dispersion liquidMicro-extraction, dispersed solid phase extraction, gel permeation chromatography, etc. By taking the advantages of the methods as a reference, researchers put forward a rapid, simple, cheap, effective, reliable and safe (QuEChERS) method in 2003, and the method has the characteristic of 'green chemistry', and becomes one of the standard sample preparation methods in the field of pesticide analysis. In the QuEChERS method, the purification process is a critical step, and the selection and use of a purification agent is the most important factor. Conventional scavengers include N-Propylethylenediamine (PSA), C₁₈Modified silica gels and Graphitized Carbon Blacks (GCB). In view of the deficiencies in the properties of these materials, researchers have developed new QuEChERS scavengers, such as ZrO₂A carbon nanotube base, a graphene base, and the like. The application of purifiers lays the foundation of the QuEChERS method, however, the purifiers are expensive and complex in preparation process, and the obtainment of a low-cost, easily-obtained and effective purification material is very important and urgent.

Disclosure of Invention

The invention aims to provide a QuEChERS method for detecting pesticide residues in foods such as vegetables, fruits and the like by using a substance with a switchable state under a mild condition as a purification material.

Aiming at the purposes, the technical scheme adopted by the invention is as follows: and (2) dehydrating the acetonitrile extraction liquid of the sample to be detected, adding a purifying agent, heating to the temperature 2-5 ℃ higher than the melting point of the purifying agent, violently shaking for 1-2 min, carrying out liquid-liquid microextraction on the dispersion liquid, freezing at-20-0 ℃ until the purifying agent is separated out and solidified, carrying out centrifugal separation or filtration, and taking the supernatant to detect the pesticide residue by using a gas chromatography-mass spectrometer.

The purifying agent contains amino and carbon chain length C in molecular structure₁₀To C₂₀The melting point of the purifying agent is 30-60 ℃, and the purifying agent is slightly soluble or insoluble in acetonitrile at the temperature of below 0 ℃; the method specifically comprises the following steps: n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-nonadecylamine, and the like.

In the method, the mass-volume ratio of the added purifying agent to the dehydrated acetonitrile extraction liquid of the sample to be detected is preferably 10-50 mg:1 mL.

In the method, the preparation method of the acetonitrile extraction liquid of the sample to be detected comprises the following steps: taking an edible part of a sample to be detected, beating the edible part of the sample to be detected into homogenate by using a juicer, sequentially adding acetonitrile, anhydrous magnesium sulfate and sodium chloride into the homogenate according to the mass-volume ratio of the homogenate to acetonitrile of 1g: 1-2 mL and the mass ratio of the serum to anhydrous magnesium sulfate and sodium chloride of 1: 0.5-1: 0.25-1, violently shaking for 1-3 min, and centrifuging to obtain a supernatant, namely acetonitrile extraction liquid of the sample to be detected.

In the above method, the method for dehydrating the acetonitrile extraction liquid of the sample to be detected comprises: adding anhydrous magnesium sulfate into acetonitrile extraction liquid of a sample to be detected, wherein the mass volume ratio of the anhydrous magnesium sulfate to the extraction liquid is 1g: 3-4 mL, oscillating for 1-3 min, and filtering or centrifuging to remove the anhydrous magnesium sulfate.

In the method, the sample to be detected is fruit or vegetable, the pesticide is any one of organophosphorus pesticides, organochlorine pesticides, pyrethroid pesticides and herbicides, wherein the organophosphorus pesticides are diazinon, malathion, methidathion, profenofos, triazophos, phosmet, vodkin, coumaphos, methylisotalophos and the like; the organic chlorine pesticide is quintozene, chlorpyrifos, triadimefon and the like; the pyrethroid pesticide is bifenthrin, fenpropathrin and the like; the herbicide is acetochlor, metolachlor and the like.

The invention has the following beneficial effects:

the invention firstly uses acetonitrile to extract the sample homogenate which is added with sodium chloride until the solubility is saturated, then anhydrous magnesium sulfate is added to remove water, then purifying agent is added, the temperature is controlled to be above the melting point of the purifying agent, the melted purifying agent and the acetonitrile extract fully react to carry out dispersion liquid micro-extraction, then the temperature is reduced to solidify the purifying agent, the solidified purifying agent which combines a large amount of impurities is separated from the extract by centrifugation or filtration, thereby achieving the purposes of removing the impurities and purifying the sample matrix, and finally the extract which is subjected to purification treatment is directly fed into a gas chromatography-mass spectrometer for detection and analysis. Compared with the traditional QuEChERS method, the invention takes the common chemical reagent which can switch the substance state under the mild condition as the purification material, and the material can remove most impurities by being used alone, thereby achieving the purification purpose; in the purification process, the action mechanism of the purification material and impurities with switchable substance states is dispersion liquid-liquid microextraction, which is different from the dispersion solid-phase extraction of the traditional purification material, so that the purification material has the characteristics of high extraction efficiency, high enrichment rate, small dosage and the like. Meanwhile, in the dispersion liquid-liquid micro-extraction, a purifying material capable of switching substance states is adopted as a purifying agent, the purifying agent can be quickly solidified at a low temperature, the purifying agent carrying a large amount of impurities is converted into a solid phase for separation, and the defect of incomplete dispersion liquid-liquid micro-extraction separation is avoided.

Drawings

FIG. 1 is a total ion flow graph (curve a) of a cucumber sample extract in a full scan mode and a total ion flow graph (curve b) of the cucumber sample extract after being purified by n-octadecylamine.

Detailed Description

The invention will be further described in detail with reference to the following figures and examples, but the scope of the invention is not limited to these examples.

The GC-MS used in the examples was an Agilent 7890B GC combined with a 5977B mass spectrometer, and the column used HP-5ms (30 m.times.0.25 mm.times.0.25 μm). Gas chromatography-mass spectrometry conditions: the carrier gas is high-purity helium (the purity is more than or equal to 99.999%), the flow rate of the carrier gas is 1.2mL/min, the initial temperature of the chromatographic column is 80 ℃, and the time lasts for 1 min; then heating to 185 ℃ at the speed of 15 ℃/min for 5 min; finally, heating to 270 ℃ at the speed of 15 ℃/min for 5 min; the sample volume was 1.0. mu.L, and no split was performed. The injection port temperature is 230 ℃, the ion source temperature is 270 ℃, the interface temperature is 280 ℃ and the quadrupole rod temperature is 150 ℃.

Example 1

Taking an edible part of fresh cucumber, beating into homogenate by using an electric juicer, adding 2g of the homogenate into a 10mL centrifuge tube, taking triphenyl phosphate as an internal standard, adding 0.1mg/kg of the amount of the homogenate, standing for 30min, then sequentially adding 2mL of acetonitrile, 1g of anhydrous magnesium sulfate and 0.5g of sodium chloride, violently shaking for 1min, centrifuging, taking 2.0mL of supernatant into a 5mL centrifuge tube, adding 0.5g of anhydrous magnesium sulfate, and shaking for 1min for dehydration. Transferring 1mL of dehydrated extract into a 2.5mL centrifuge tube containing 20mg of n-octadecylamine, heating to 55 ℃, and violently shaking for 1min to perform dispersion liquid-liquid microextraction; then freezing for 5min at-10 ℃, centrifugally separating, taking 1.0 mu L of supernatant fluid to enter a gas chromatography-mass spectrometer to measure the pesticide residue. The blank was also prepared with the sample without n-octadecylamine, and the results are shown in FIG. 1. As can be seen from FIG. 1, compared with curve a, the impurity peak in curve b is significantly reduced and weakened, i.e. after n-octadecylamine purification treatment, the impurities in the extract are significantly reduced. This shows that n-octadecylamine has excellent impurity removal capability, and the QuEChERS method using n-octadecylamine as a purifying agent can effectively reduce the influence of matrix effect.

To demonstrate the beneficial effects of the present invention, the inventors carried out a spiked recovery test using the method of example 1 for 16 pesticides (organophosphate pesticides: diazinon, malathion, methidathion, profenofos, triazophos, phosmet, fluvothion, coumaphos and methylisothiafos; organochlorine pesticides: quintozene, chlorpyrifos and triadimefon; pyrethroid pesticides: bifenthrin and fenpropathrin; herbicides: acetochlor and metolachlor) in cucumber, orange, apple, capsicum, lettuce and tomato with a spiked amount of 100ng/g, wherein each sample was assayed in triplicate. The retention times and mass-to-charge ratios of the 16 pesticides and the internal standard triphenyl phosphate (the first of which is the quantitative ion) are shown in table 2, the recovery rates and Relative Standard Deviations (RSD) of the 16 pesticides are shown in table 2, and the relative standard deviations are shown after the addition and subtraction of the numbers in table 2.

TABLE 1

TABLE 2

As can be seen from Table 2, when the standard addition amount is 100ng/g, the recovery rate of 16 pesticides in cucumber, orange, apple, pepper, lettuce and tomato is 83.2% -117.4%, and the relative standard deviation is 1.2% -12.6%, which indicates that the method has good accuracy and repeatability and is suitable for detecting common pesticides in vegetables and fruits.

Claims

1. A QuEChERS method for detecting pesticide residues based on purifying agent state switching is characterized by comprising the following steps: dehydrating the acetonitrile extraction liquid of a sample to be detected, adding a purifying agent, heating to a temperature 2-5 ℃ higher than the melting point of the purifying agent, violently shaking for 1-2 min, carrying out liquid-liquid microextraction on the dispersion liquid, freezing at-20-0 ℃ until the purifying agent is separated out and solidified, carrying out centrifugal separation or filtration, and taking the supernatant to detect the pesticide residue by using a gas chromatography-mass spectrometer;

the purifying agent contains amino and carbon chain length C in molecular structure₁₀To C₂₀The melting point of the purificant is 30-60 ℃, and the purificant is slightly soluble or insoluble in acetonitrile below 0 ℃.

2. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 1, characterized in that: the purifying agent is any one of n-hexadecylamine, n-heptadecylamine, n-octadecylamine and n-nonadecylamine.

3. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 2, characterized in that: the mass-volume ratio of the addition amount of the purifying agent to the dehydrated acetonitrile extraction liquid of the sample to be detected is 10-50 mg:1 mL.

4. The QuEChERS method for pesticide residue detection based on depurative state switching according to any one of claims 1 to 3, which is characterized in that: the preparation method of the acetonitrile extract liquid of the sample to be detected comprises the following steps: taking an edible part of a sample to be detected, beating the edible part of the sample to be detected into homogenate by using a juicer, sequentially adding acetonitrile, anhydrous magnesium sulfate and sodium chloride into the homogenate according to the mass-volume ratio of the homogenate to acetonitrile of 1g: 1-2 mL and the mass ratio of the serum to anhydrous magnesium sulfate and sodium chloride of 1: 0.5-1: 0.25-1, violently shaking for 1-3 min, and centrifuging to obtain a supernatant, namely acetonitrile extraction liquid of the sample to be detected.

5. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 4, wherein: the method for dehydrating the acetonitrile extract of the sample to be detected comprises the following steps: adding anhydrous magnesium sulfate into acetonitrile extraction liquid of a sample to be detected, wherein the mass volume ratio of the anhydrous magnesium sulfate to the extraction liquid is 1g: 3-4 mL, oscillating for 1-3 min, and filtering or centrifuging to remove the anhydrous magnesium sulfate.

6. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 1, characterized in that: the sample to be detected is fruit or vegetable.

7. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 1, characterized in that: the pesticide is any one of organophosphorus pesticide, organochlorine pesticide, pyrethroid pesticide and herbicide.

8. The QuEChERS method for pesticide residue detection based on scavenger state switching according to claim 7, wherein: the organophosphorus pesticide is any one of diazinon, malathion, methidathion, profenofos, triazophos, phosmet, futhion, coumaphos and methyl isosalix; the organic chlorine pesticide is any one of quintozene, chlorpyrifos and triadimefon; the pyrethroid pesticide is bifenthrin or fenpropathrin; the herbicide is acetochlor or metolachlor.